Which should I use as the main router? N66U and AC68U

Currently I have two N66Us wired together, one as the main router and one running in AP mode. I'd like to add an AC68U as an additional wired AP. Is there any reason I should make the AC68U my main router and not an AP? The reasoning behind using it as an AP is that the room where it would be located is where most of our wifi traffic is, while my current N66U router is not centrally located (2nd floor corner office) due to the location of the best incoming coax.

Thanks in advance!